Japan Coast Guard vessels sail along with Chinese surveillance ship Haijian No. 66 (r.) near disputed islands called Senkaku in Japan and Diaoyu in China, seen in background, in the East China Sea, on Monday, Sept. 24.

Taipei, Taiwan — The United States is urging Asian leaders to cool increasingly heated territory disputes in the Asia Pacific – with good reason, say analysts.

The US has intense interest in Asian leaders working things out peacefully. Competing claims to islets or swaths of ocean could disrupt trade – or worse, cut off lanes used by American commercial shippers, as well as the US Navy.

Senior American officials have visited Asia twice this month alone, to the chagrin of China, urging calm in a region where maritime clashes have become a nearly daily threat since April.

“The United States will try to keep everyone in check, sending the message that ‘this is the line you don’t want to cross,' ” says Alex Chiang, associate professor of diplomacy at National Chengchi University in Taipei. “The United States doesn’t want to see China become more powerful and more influential in the region.”

Vessels from Japan, China, and Taiwan have squared off this month over eight uninhabited islets 137 miles from Taipei but controlled by Tokyo. The dispute has driven tens of thousands of Chinese to join anti-Japan demonstrations.

Beijing also claims the 1.4 million square-mile South China Sea – rich in fisheries as well as undersea oil and gas. In April it entered a tense standoff with the Philippines over rights to part of the ocean. Malaysia, Taiwan, and Vietnam claim all or part of the South China Sea as well.

Then there is the matter of the US being obligated by security pacts or acts of Congress to help defend Japan, Taiwan, and the Philippines – all located off the east coast of rising military power and US cold-war rival China. But today the US also needs China, a low-cost manufacturing base and major market for US exports. An open conflict among disputants could throw US trade, shipping, and naval exercises out of whack.

US officials may be giving leaders of its smaller allied nations in Asia detailed suggestions in private on how to work out differences with China, says Nathan Liu, international affairs professor at Ming Chuan University in Taiwan. “That means the US is going to continue a containment policy from when China was behind the Iron Curtain, but since [China's] opening it needs to make sure they have a voice in international affairs," he says. "They also want to make sure US interests in the region are protected.”

Treaties bind the US to Japan, Taiwan, and the Philippines

After World War II, when Japan was weak and communist China seen as a threat, the US government gave many former frontline islets to Japan or put them under its own protection.

A 1951 Security Treaty still requires the US to back up Japan during an attack, and a US-Japanese agreement in 1971 gave administrative rights over the eight inhabited East China Sea islets to Tokyo, which calls them the Senkaku. A Mutual Defense Treaty, also signed in 1951, obligates the US to support the Philippines militarily, while a 1979 act of Congress says the US government must consider the defense needs of Taiwan if that island comes under fire.

China is seen as the most likely aggressor toward all three. Yet it is the US's second-largest trade partner, after the European Union, with two-way trade totaling $539 billion last year.

“If armed force [was] used to resolve the conflicts, there would almost certainly be a negative effect on US-China trade and East Asian regional economic development and integration,” says Scott Harold, associate political scientist with the American think tank RAND Corp. “No one would win from a nonpeaceful outcome.”

Still, China has rebuffed US advice that it cooperate more with other South China Sea claimants, and anti-Japan activists are ready to protest against the US if Beijing accuses it of backing Japan in the East China Sea.

"If China believes that the US government has stuck its hand in the dispute, then it should take that up with the US side,” says Zhang Likun, member of the China Federation to Protect the Diaoyu Islands, China’s name for the Senkaku.

Washington relies on international conventions, which allow American ships to pass through the massive exclusive economic zones of Asian countries seeking more control over the seas, Mr. Harold says. International laws could be eroded only if one claimant forced others out of its zone.

About half the world’s shipping traffic passes through the South China Sea, and US vessels make up a large portion of that traffic. By 2020, some 60 percent of US naval ships will be based in the Pacific, part of a “pivot to Asia” policy formulated from last year.

“If a dispute escalates, insurance rates for shipping will spike, and that will affect the US and other countries,” says Bonnie Glaser, a senior fellow with the CSIS Freeman Chair in China Studies. “If tankers could not safely pass through those waters, supply of oil to Japan, a key US ally, would be threatened.”